JPH11214603A - Lead frame and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a lead frame for which a sectional shape is satisfactory, both a tape sticking part and a plating surface are flat, and the reliability of tape sticking to a semiconductor device is high. SOLUTION: Coining is performed on the tip part of an inner lead 7a, from both surfaces of the lead. Through the coining, burrs at punching out the lead and slant on a sagging surface side are canceled, and planarity of a bonding part and a tape sticking surface are ensured. After working distortion is canceled by conducting annealing, a linkage part 9 of the lead chip is cut off. At this time, a burr 12 is further generated at the tip of the inner lead 7a, so that secondary coining is performed for crushing the burr 12. A plating 13 is performed on a single side of a coining part, and a tape 8 is stuck on the back of the coining part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame used for a semiconductor device having a LOC (Lead On Chip) structure applied to a semiconductor device such as a memory, and in particular, a tape for mounting a semiconductor element on a tip of a lead is attached. The present invention relates to a lead frame of a type to be attached and a manufacturing method thereof.

[0002]

2. Description of the Related Art DRAM (Dynamic Random Access Memory)
Press processing (stamping method) using a progressive die is usually used for shape processing of a lead frame used for assembling a semiconductor device such as ry).

FIG. 3 shows an outline of a general punching die. The plate 6 is first clamped between the stripper 3 and the die 4, and the plate pressing force at this time is given by the spring 1 arranged above the stripper 3. Generally, a fine pattern such as a lead frame is punched using a progressive die, so that the left and right sides of the lead are punched at different stages.

FIG. 4 is an enlarged view of the punched portion shown in FIG. The entire upper mold 2 of FIG. 3 is lowered, and the punch 5 of FIG.
First punching is performed between the die 4 and the die 4. Next, the plate material 6 is fed and the other side is punched to form a lead. FIG. 5 shows a state of a cross section of the lead 7 at the time of punching after the lead is formed.

[0005]

However, since the left and right sides of the lead 7 are punched at different stages, when the pattern is miniaturized, the lead 7 is shown in FIG. As described above, it is pulled by the punch 5 and rotated, and it becomes difficult to keep the cross-sectional shape of the square.

Generally, at the time of punching, the material is drawn in by the punch 5, so that the surface of the material on the punch side is inclined. At the time of punching after the lead 7 is formed,
In order to prevent the rotation of the lead 7, the strip 7 is normally pressed down.

However, when the lead width is reduced, the contact area of the upper surface of the lead with the stripper 3 is reduced due to the drooping of the upper surface of the lead, which prevents the material from being pulled in. Thus, the cross-sectional shape of the lead 7 deteriorates.

In a lead frame used for a semiconductor device having a LOC structure as shown in FIG. 6, in which a tape 8 is attached to the tip of a lead of an inner lead 7a, a chip (not shown) is provided on the surface of the tape 8. Is mounted. Therefore, the reliability of the adhesion between the tape 8 and the lead frame is extremely important.

However, in the lead frame having the LOC structure, the burr-side surface of the inner lead 7a is plated by coining for securing a flat width required for wire bonding, and then plated. Is left untreated on the side of the side where the is attached. For this reason, when the lead width is small on the surface on the side where the tape is attached, the inclination of the lead becomes large, and the reliability of the tape adhesion is reduced.

Further, in the conventional manufacturing method, since the tip of the inner lead is released and coining is performed, the lead rotates even if coining is performed from both sides, and the inclination of the whol side and the burr side can be improved. Did not.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art, to have a good cross-sectional shape, to have a flat tape-attached portion and a flat plated surface, and to have a high reliability of tape-attaching to a semiconductor device. An object of the present invention is to provide a lead frame and a manufacturing method thereof.

[0012]

In order to achieve the above object, a lead frame according to the present invention comprises a lead frame used in a semiconductor device having a LOC structure, in which both ends of inner leads are coined, and one side is plated. Tape is attached to the opposite surface (claim 1).

Coining for expanding the lead width and maintaining flatness is usually performed on one side of the tip of the inner lead in order to facilitate wire bonding, and this is plated. In the present invention, coining is further performed on the tape application surface side of the tip of the inner lead, and the tape is applied on the surface. Therefore, according to the present invention, it is possible to obtain a lead frame in which the inner lead has a good cross-sectional shape, has both a tape-attached portion and a plated surface flat, and has high tape-attachment reliability.

Further, according to the method of manufacturing a lead frame of the present invention, there is provided a method of manufacturing a lead frame used for a semiconductor device having a LOC structure, wherein a step of punching an inner lead side surface and a step of forming a connecting portion in a state where the lead ends are connected in common. Further, a step of punching a relief hole in a portion on the tip side so as to absorb a change in lead size, a step of coining both sides of the lead tip, an annealing step of releasing distortion due to the punching and coining, and a connecting portion of the lead tip , A coining step of crushing burrs at the tip of the lead caused by the release, a step of plating one side of the coining part, and a step of attaching a tape to the back side of the coining part. 2).

By punching out the side surface of the inner lead and subsequently punching out the relief hole at a further portion of the tip of the inner lead, a droop occurs on one surface of the inner lead and burrs are generated on the opposite surface. The burrs and slant on the dripping side during punching of the lead are eliminated by performing coining from both sides of the lead in the next process, and the flatness as a bonding part on one side of the inner lead and the opposite side of the inner lead The flatness of the tape assuring surface is secured. In addition,
During the coining process, the lead is elongated, but this is absorbed by a relief hole formed further ahead of the tip of the lead.

After the punching and coining of the inner lead are completed, an annealing step is performed to eliminate these processing distortions. Thereafter, the lead tip is removed to disconnect the connection between the leads. At this time, since burrs are further generated by cutting off the tip, a second coining is performed to crush the burrs. After the completion of the coining, plating and tape sticking are performed to complete the lead frame.

By doing so, not only the plating surface but also the flatness of the tape application surface is improved, so that the tape application reliability is improved.

Further, the lead frame manufactured by this manufacturing method (claim 3) is suitable as a lead frame used for a semiconductor device having a LOC structure such as a memory.

As the tape, for example, a tape provided with an adhesive layer on both sides of an insulating tape such as polyimide is used.
Alternatively, a tape consisting of only an insulating adhesive layer may be used.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a lead frame according to the present invention will be described with reference to the drawings. Here, as a lead frame to be manufactured, a type having a LOC structure shown in FIG. 6 and a tape 8 for mounting a semiconductor element attached to the tip of a lead 7 is exemplified.

1 and 2 show a manufacturing process of a lead frame according to the present invention.

First, a plate material, which is a strip-shaped material, is placed in a progressive die, and the side edges of the inner leads 7a and the outer leads of the leads 7 in the lead frame shown in FIG. 6 are sequentially formed. That is, first, as shown in FIG. 1A, only the side surfaces of the inner lead 7a are punched out while the tips of the inner leads 7a are commonly connected by the connecting portion 9 (inner lead punching step).

Next, as shown in FIG. 1 (b), in a state where the tips of the inner leads 7a are commonly connected, the lead size is added to a portion further beyond the tip of the inner lead, that is, the connecting portion 9 at the tip of the inner lead. Escape hole 1 to absorb the change
0 is punched (inner lead tip punching step).

In the next step (FIG. 1 (c)), coining is performed on the tip of the inner lead 7a from both sides of the lead. The flatness of the part and the tape application surface is ensured (coining process). In FIG. 1C, the area 11 on which the coining has been performed is shown as a hatched portion. During the coining process, the lead 7 is extended, but this is absorbed by the relief hole 10 which is a punched portion further ahead of the lead tip.

In this example, the first coining performed on both sides of the lead tip is, as shown by the cross section (a) in FIG. 1C, a portion of the tip of the inner lead 7a just before the connecting portion 9, that is, It is applied only to the tip portion not including the connecting portion 9. This is because the processing area is small, so that the load on the mold is small, and the influence on other punching regions and the like can be reduced. However, as shown by the cross section (b) in FIG. 1C, coining may be performed including the region of the connecting portion 9 to make the same flat surface.

After the punching and coining of the inner lead are completed, an annealing step is performed to eliminate these processing distortions (not shown). The annealing step at this time may be a known general method.

After that, the leading end of the lead is removed to release the connecting portion 9 at the leading end of the inner lead, and FIG.
As shown in (5), the connection between the inner leads 7a is disconnected (lead connection / disconnection step).

At this time, since the burrs 12 are further generated at the tips of the inner leads due to the separation of the tips of the inner leads, the second coining is performed to crush the burrs 12. That is, as shown in FIG. 2E, coining is performed on the burr side surface at the tip of the inner lead 7a, thereby returning the tape application surface to a flat surface (lead tip coining step).

After completion of the coining, a noble metal plating 13 is applied to the bonding portion formed on one surface of the tip of the inner lead 7a as shown in FIG. 2 (f) (plating process). Also, as shown in FIG. 2 (g), the inner leads 7a
The tape 8 on the tape affixed surface formed on the opposite side of the tip of
Are commonly attached to the tips of the inner leads, and the inner leads are connected to each other (tape attaching step). Thus, a lead frame with no lead shift and no lead bending is completed with a narrow pitch press lead frame.

[0030]

As described above, according to the present invention, the following excellent effects can be obtained.

(1) According to the first or third aspect of the present invention, coining is performed on both surfaces of the tip of the inner lead, plating is performed on one surface, and tape is adhered on the opposite surface. The lead frame for a LOC structure having a good cross-sectional shape, a flat tape-attached portion and a plated surface, and a high reliability of tape-attachment can be obtained.

(2) According to the second aspect of the present invention, the step of punching the inner lead side surface and the step of punching out the relief hole and then the step of performing coining on both sides of the lead tip are provided. Since the inclination of the side is eliminated, flatness as a bonding portion is secured on one surface of the inner lead, and flatness as a tape attachment surface is secured on the opposite surface of the inner lead. Further, a coining step is provided next to the step of releasing the connection part of the lead tip, so that burrs generated by cutting off the tip are eliminated.Accordingly, according to the lead frame manufacturing method of the present invention, the plating surface of the inner lead tip and The flatness of the drooping surface can be improved, and the reliability of affixing the tape, such as for a LOC structure, can be dramatically improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first half of a manufacturing process of a lead frame of the present invention.

FIG. 2 is a diagram showing the latter half of the manufacturing process of the lead frame of the present invention.

FIG. 3 is a sectional view showing a general mold structure.

FIG. 4 is an enlarged view of a lead punched portion.

FIG. 5 is a view showing a state of a punching portion at the time of rear punching.

FIG. 6 is a view showing the appearance of a general LOC structure lead frame.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spring 2 Upper die 3 Stripper 4 Die 5 Punch 6 Plate material 7 Lead 7a Inner lead 8 Tape 9 Connection part 10 Relief hole 11 Coined area 12 Burr 13 Plating

Continued on the front page (72) Inventor Ryuji Yonemoto 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Hitachi Cable, Ltd.

Claims (3)

[Claims] 1. A lead frame used for a semiconductor device having a LOC structure, wherein coining is performed on both surfaces of the tip of an inner lead, plating is applied on one surface, and tape is applied on the opposite surface. 2. A method of manufacturing a lead frame used for a semiconductor device having a LOC structure, wherein a step of punching a side surface of an inner lead and a change in lead size are further added to a portion of the connecting portion further in a state where the leading ends of the leads are commonly connected. Punching a relief hole so as to be able to absorb the heat, a step of coining both sides of the lead tip, an annealing step of releasing the distortion caused by the punching and coining, and a step of releasing a connection part of the lead tip. A method for manufacturing a lead frame, comprising: a coining step of crushing a burr at a tip end of a lead, a step of plating one side of the coining section, and a step of attaching a tape to the back side. 3. A lead frame manufactured by the manufacturing method according to claim 2.